Method and device for measuring a physical variable

• US 6,324,910 B1
• Filed: 06/22/1999
• Issued: 12/04/2001
• Est. Priority Date: 10/21/1996
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Schilp, Andrea, Kulcke, Hans-Martin, Funk, Karsten, Laermer, Franz
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): FAYYAZ, NASHMIYA SAQIB
• Application Number:
  US09/284,907
• Time in Patent Office: 896 Days
• Field of Search: 735/041.2, 735/141.6, 735/040.4, 735/141.8, 735/79
• US Class Current: 73/579
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A method for measuring a physical variable in which a structure is put in resonant oscillations and a change in the oscillation frequency of the structure as a result of a change in the physical variable to be measured is detected, and a frequency-analog signal is provided. A structure oscillating with a resonance frequency receives an electrostatic force.

Claims

1. A method for measuring a physical variable, comprising the steps of:

oscillating a structure in a particular oscillation direction at a resonant frequency using a drive mechanism;

providing, to the structure, an additional electrostatic force, the additional electrostatic force being separate from the drive mechanism and acting in a direction substantially parallel to the particular oscillation direction;

detecting a change in a frequency at which the structure oscillates, the frequency change corresponding to a change in the physical variable to be measured; and

providing a frequency-analog signal as a function of the frequency change.

2. The method according to claim 1, wherein the additional electrostatic force can be changed.

3. The method according to claim 1, wherein the step of oscillating the structure includes the steps of assigning a counterstructure to the structure, applying a constant voltage between the counterstructure and the structure, and changing a spacing between the structure and the counterstructure.

4. The method according to claim 3, further comprising the step of:

setting a spacing between an operating point and a point of mechanical instability via a level of the constant voltage.

5. The method according to claim 3, further comprising the step of:

electronically compensating for a change in the spacing between the structure and the counterstructure as a result of a resonance oscillation of the structure.

6. The method according to claim 3, wherein the spacing between the structure and the counterstructure is changed by an effect of the physical variable to be measured.

7. A device for measuring a physical variable, comprising:

a structure having a resonant frequency;

a counterstructure coupled to the structure, the structure and the counterstructure both being connected to a voltage source, the counterstructure providing an electrostatic force that acts on the structure;

a drive mechanism for oscillating the structure at the resonant frequency, the drive mechanism being separate from the electrostatic force provided by the counterstructure and acting in a direction that is substantially parallel to a direction in which the electrostatic force acts; and

an evaluation device for detecting an oscillation frequency of the structure, the oscillation frequency of the structure being a function of at least the physical variable.

8. The device according to claim 7, wherein the counterstructure is movably mounted.

9. The device according to claim 7, wherein the voltage source provides a constant voltage.

10. The device according to claim 7, wherein the counterstructure is a movably mounted component in an acceleration sensor.

11. The device according to claim 7, wherein the device is used in an acceleration sensor, and wherein the structure and the counterstructure are arranged such that the structure and the counterstructure form an angle with a sensitivity direction of the acceleration sensor.